Why sugar could be to blame for your bad memory – and can it get you hooked?

Liam Mannix

To tell the story of what sugar does to your brain, you have to start with the thought that triggers your need for a hit of sweetness.

It often happens in the afternoon when your brain, which runs on sugar, starts to get hungry.

To satiate the craving your brain activates a string of neurons, often referred to as the reward pathway, which pump the chemical dopamine into your brain.

All of a sudden you need a chocolate bar or that sweet pastry you saw at lunchtime.

If you act on that craving, the reward pathway then switches mode, pumping chemicals such as beta-endorphins into your brain, generating feelings of pleasure.

The part of the brain that senses hunger is also integrated into the rewards system.

“We need to eat more to get the same feeling. That’s a classic feature of addiction.” Dr Zane Andrews

Your brain thanks you for the sugar hit by making the chocolate bar literally taste sweeter, says Dr Zane Andrews, a scientist at Monash University who studies how our brains regulate control of our diets.

But if you respond to the brain’s need for sugar too often, the reward pathway can develop tolerance to the stimulus.

“That means we need to eat more to get the same feeling. That’s a classic feature of addiction,” says Dr Andrews.

The prefrontal cortex acts as the brain's “brakes” but it's weakened by too much sugar (and fat).

Crumbling willpower

You do possess the ability to resist cravings - it’s called willpower.

That ability to stop yourself comes in part from a network of neurons called inhibitory neural circuits. These circuits occur throughout your brain, but are particularly concentrated in the parts involved in decision-making, impulse control and delaying gratification.

But if you find you can’t resist that craving for a chocolate bar don’t be ashamed – you may be able to blame it on the sugar.

In world-first research using rats, Dr Reichelt has shown that high-sugar diets can alter decision-making and the ability to control behaviour.

Her studies revealed that rats fed on high-sugar diets suffered a loss of those willpower neurons.

“When you’re consuming these high-sugar diets and you’re told to stop consuming them, you’ve made alterations to your behavioural control – and that can lead to your diet falling apart,” she says. “You’re literally unable to resist that cake.”

Much of the research, though, on sugar’s impact on the brain has yet to be replicated in people.

In another study conducted last year, a team led by Professor Richard Stevenson from Macquarie University asked a group of volunteers to rate how much they wanted to eat several snack foods when they were feeling hungry versus when they were sated.

They found that the volunteers who regularly ate a high-fat, high-sugar diet were much more likely to crave snack foods even when they weren’t hungry.

The scientists suggest the high-sugar and fat diet was actually impairing the ability of the brain to block food cravings.

Nicotine, alcohol, sugar – the desire for them is also linked to the part of the brain that registers fear and stress.

“We’re all prone to try to excuse our behaviour by claiming we’re addicted. Which is rubbish.”Professor Margaret Morris

Can you get hooked on sugar?

Let’s say you manage to use your willpower to get on top of your craving for that chocolate bar. But the feeling does not go away.

Your mouth runs dry. You can taste the first bite. Your work performance drops. It’s just like ... (you think wistfully to yourself) ... craving a cigarette.

Maybe the similarities run deeper than that.

In world-first research, Queensland University of Technology neuroscientist Professor Selena Bartlett claims to have found evidence that high-sugar diets act on the brain in very similar ways to tobacco, alcohol or other physically addictive substances.

Her work targets the basolateral amygdala, a small region in the brain that is linked to fear and stress, and the prefrontal cortex, which sits at the front of the brain.

She found that mice who had binged on sugar had far fewer links between the neurons in these regions and looked a lot like animals addicted to alcohol.

More remarkably, when her researchers gave mice a medication used to treat nicotine addiction, they stopped eating as much sugar.

“What we discovered in the last five years is that sugar is as addictive as alcohol. We nailed a very specific set of circuits in the brain that alcohol and nicotine bind to,” Professor Bartlett says.

“We showed sugar using the same protocols could change the brain in exactly the same way as alcohol and nicotine do, which labels it into the addictive pathway.”

In a hotly contested field, claims about sugar’s addictive qualities are among the most fraught.

“When we look at obesity, we’re not finding those addictive qualities at all. Where’s the evidence for that?,” says Professor John Dixon, a researcher with the Baker Heart and Diabetes Institute.

“More than any other disease, people believe they know what causes obesity. They don’t.”

Even University of NSW Professor Margaret Morris, one of the leading proponents of the theory that sugar can damage the brain, says the evidence for actual addiction is weak.

“We did a review of the evidence and we had to conclude, on the balance of evidence, that there was no strong evidence for sugar addiction in humans.

“We’re all prone to try to excuse our behaviour by claiming we’re addicted. Which is rubbish.”

In animals, and men and women, a high-sugar diet seems to impair the hippocampus, which controls memory.

“Sugar seems to adversely impact the hippocampus and longer-term brain structures that are involved in decision-making and pleasure.”Professor Richard Stevenson

I can’t forget but I don’t remember what

Most research on sugar’s impact focuses on a small horseshoe-shaped region in the middle of the brain, about level with your ear, called the hippocampus. It is responsible for memory formation and navigation; to do that, it needs to be continually building new neurons or rewiring existing pathways.

This role makes it vulnerable to external stresses – potentially such as diets high in sugar.

In animals, the research is fairly clear: sugar damages their ability to make new memories.

The first person to confirm that effect in humans was Professor Richard Stevenson, leading a team at Macquarie University, earlier this year.

He had volunteers spend a week eating a high-fat, high-sugar breakfast. After just four days, their performance on memory tests fell dramatically.

“Sugar seems to adversely impact the hippocampus and longer-term brain structures that are involved in decision-making and pleasure,” he says.

The University of Sydney’s Dr Kieron Rooney once did a quick study – largely for a lark – on a small group of people who signed up to a popular quit sugar diet. He was surprised to find that their memories had significantly improved by the end of the diet.

Professor Morris has spent more than 20 years putting rats on high-sugar diets. She says the results are consistent and repeatable. “Weight gain and a cognitive decline - it’s quite a large effect,” she says.

Obesity is characterised by low-grade inflammation throughout the body. The theory, says Professor Morris, is that with excess sugar and fat in the diet inflammation also appears to affect the hippocampus, impairing its function.

High-sugar diets also reduce the levels of a chemical needed for new neuron formation - which is crucially important to the hippocampus’s job of creating new memories.

The most prominent and studied impact of sugar on the hippocampus is navigation. We use the hippocampus to build an internal map of our surroundings.

Professor Morris found that navigation for rats fed a high-sugar diet is significantly impaired.

She also makes it clear though that her research on sugar’s effects on the brain has not been replicated in people, so the link to how humans will react is not definite.

The green flecks are new immature neurons in the hippocampus of a mouse but their number has been reduced by chronic sugar consumption. Photo: Courtesy Dr Arnauld Belmer, QUT

The amount of newborn neurons (green) is much higher in the brain of a mouse fed a normal diet. Photo: Courtesy Dr Arnauld Belmer, QUT

What can we do?

So, what can you do to protect your brain from sugar?

Beyond trying to eat less of it, not much, experts say.

To deal with the addictive powers of sugar, Professor Selena Bartlett suggests meditation exercises to build focus and willpower.

Omega-3s, the fats contained in fish oil, have shown potential neuro-protective effects in some trials, plus the ability to bolster hippocampal function. Professor Morris suggests using them to supplement your diet.

But ultimately, says Professor Morris, the only magic pill is exercise and following the Australian Dietary Guidelines, which recommend limiting your intake of added sugars.

“There is no question that there is some ability of the system to reset. If people adopt a healthy diet, that could go some way to reversing the effect.”

Gents, just finishing day 5 of going gluten and sugar free. Its actually been pretty easy so far surprisingly, no mad cravings yet.

However I have felt pretty lethargic and feeling more tired than normal. Is that my body working the shit out of the system and it adapting to its new energy sources? Hopefully it pisses off soon

Keep fighting the good fight men!

After a week or two I feel more energetic. I've just quit gluten, dairy and sugar and I'm feeling good after 2 very pure days. Though it's different for everybody, though make sure you drink LOTS of water.

Pretty tough cutting simple sugars and gluten for me, to run an hour everyday and then get home and snack on something to get some energy without too much effort.

Weekends are the worst as it is so easy to just grab a snack bar, cookies or some shit.

If anyone is in the same boat, get a few ingredients like Erythritol, Almond & Coconut flour, salted butter, cocoa powder etc., and bake a bunch of low carb snacks like keto brownies/bombs anf almond and yogurt bread to keep around the house. So you can have your cake and eat it too : )

I use Erythritol over Xylitol mainly because the latter is DEADLY to dogs with with a higher GI and carbs:

Holy crap five days seems extreme Native. Apologies if this has been explained earlier, I'm aware of the benefits of fasting for a day and intermittent fasting but what are the benefits of fasting five days?

Fasting for extended periods are beneficial on a cellular level. After three days when your body get over its starvation mode and will start to "cleanse" your system, removing toxins, resetting your immune system and actually looking for things in your body to repair breaking down old cells, instead of just digesting all the food all the time.

I do a 19/5 intermittent eating plan for most of the week but will have a smoothie or something liquid if I feel like it in the morning, but pretty much consume 2000-3000 low carb calories, depending on exercise, between 15h00 and 20h00 only. Most running and workouts are done fasted effectively but you are not using the energy from something you just ate a few minutes ago anyway.

Just thought I'd bump this thread to see how all my fellow sugar-stoppers are going? Still all good from my end. Sweets, desserts, chocolates are a distant memory. A thing of the past. Don't really miss them now. The thing I probably do miss the most is bread, but that's because so much of the convenient, fast food in our society revolves around bread. Going bread-free essentially means f**king around to eat.

There was a telly programme last night on the BBC about internet addiction, how the same dopamine pathways are involved, and that you can have too much, i.e. there is a safe level. But what was that level? It was not a figure in hours per week, it was 'when it starts to have a detrimental effect on you' which varies according to your circumstances. Annoying for those that want black and white guidance, less annoying for those that are honest with themselves and will take responsibility for their own actions.

There was a telly programme last night on the BBC about internet addiction, how the same dopamine pathways are involved, and that you can have too much, i.e. there is a safe level. But what was that level? It was not a figure in hours per week, it was 'when it starts to have a detrimental effect on you' which varies according to your circumstances. Annoying for those that want black and white guidance, less annoying for those that are honest with themselves and will take responsibility for their own actions.

Sugar cravings are a bit different, IMO, because so much of the sugar we consume has been added to foods that we wouldn't normally associate with being sugar-laden. For eg bread, buns and sauces. People know when they are consuming the internet, but they don't always know when they are consuming sugar in high quantities.

There was a telly programme last night on the BBC about internet addiction, how the same dopamine pathways are involved, and that you can have too much, i.e. there is a safe level. But what was that level? It was not a figure in hours per week, it was 'when it starts to have a detrimental effect on you' which varies according to your circumstances. Annoying for those that want black and white guidance, less annoying for those that are honest with themselves and will take responsibility for their own actions.

Sugar cravings are a bit different, IMO, because so much of the sugar we consume has been added to foods that we wouldn't normally associate with being sugar-laden. For eg bread, buns and sauces. People know when they are consuming the internet, but they don't always know when they are consuming sugar in high quantities.

Just thought I'd bump this thread to see how all my fellow sugar-stoppers are going? Still all good from my end. Sweets, desserts, chocolates are a distant memory. A thing of the past. Don't really miss them now. The thing I probably do miss the most is bread, but that's because so much of the convenient, fast food in our society revolves around bread. Going bread-free essentially means f**king around to eat.

up and down month, can cut sugar out easily weekdays but come the weekend and drinking I find it difficult to avoid when drunk/hungover.

There was a telly programme last night on the BBC about internet addiction, how the same dopamine pathways are involved, and that you can have too much, i.e. there is a safe level. But what was that level? It was not a figure in hours per week, it was 'when it starts to have a detrimental effect on you' which varies according to your circumstances. Annoying for those that want black and white guidance, less annoying for those that are honest with themselves and will take responsibility for their own actions.

Sugar cravings are a bit different, IMO, because so much of the sugar we consume has been added to foods that we wouldn't normally associate with being sugar-laden. For eg bread, buns and sauces. People know when they are consuming the internet, but they don't always know when they are consuming sugar in high quantities.

And the internet doesn't give you a fatty liver and stress your pancreas either.

There was a telly programme last night on the BBC about internet addiction, how the same dopamine pathways are involved, and that you can have too much, i.e. there is a safe level. But what was that level? It was not a figure in hours per week, it was 'when it starts to have a detrimental effect on you' which varies according to your circumstances. Annoying for those that want black and white guidance, less annoying for those that are honest with themselves and will take responsibility for their own actions.

Sugar cravings are a bit different, IMO, because so much of the sugar we consume has been added to foods that we wouldn't normally associate with being sugar-laden. For eg bread, buns and sauces. People know when they are consuming the internet, but they don't always know when they are consuming sugar in high quantities.

you mean stupid people right?

Well, is this high sugar ketchup, significant sugar-added pasta sauce, or sugar-free (just a bit of salt) tomato puree

As for me, I've just hit 230lbs, down from 250 in October. Haven't fully cut either, but am doing fine with two pieces of bread per day for a sandwich, lots of veg, a piece of fruit or two, and one sweet less than 100 cals if I feel like and an occasional bowl of air-popped popcorn (I tend to go for a hard caramel that lasts a while).

Walk to work most days (only a 30-40 min round trip depending on which of two schools I'm at), and do two upper body / one lower body workouts that last between 30-40 mins.

I'm rather shocked (and pleased) that it's been so relatively 'easy'. Cutting food, with high sugar intake making me want more, has been more effective than doing probably upwards of 10-15 hours of 'cardio' a week in the summer (long bikes and canoe trips at a good pace), and eating at least or over 2000 cals a day.

There was a telly programme last night on the BBC about internet addiction, how the same dopamine pathways are involved, and that you can have too much, i.e. there is a safe level. But what was that level? It was not a figure in hours per week, it was 'when it starts to have a detrimental effect on you' which varies according to your circumstances. Annoying for those that want black and white guidance, less annoying for those that are honest with themselves and will take responsibility for their own actions.

Sugar cravings are a bit different, IMO, because so much of the sugar we consume has been added to foods that we wouldn't normally associate with being sugar-laden. For eg bread, buns and sauces. People know when they are consuming the internet, but they don't always know when they are consuming sugar in high quantities.

you mean stupid people right?

Well, is this high sugar ketchup, significant sugar-added pasta sauce, or sugar-free (just a bit of salt) tomato puree

If you look at the label it will tell you how much sugar it contains.

btw sugar-free tomato puree would have had the sugar removed and I would imagine taste pretty awful.

I'm fairly sure I've an addiction to sugar. Can occasionally cut down but I'm back to binging every night and sometimes lunchtime too, at the moment it's 3 or 4 chocolate bars in a few minutes. Eat relatively healthily otherwise but once I get a craving for it I'll go out of my way to buy it, live too close to shops that not keeping stocking doesn't help. Always strikes after a meal, usually in the evening but lately at lunch too. I've wondered if going on one of those retreats would work in resetting things but most likely just be straight back to junk food after a night on the beer. Went a week without internet before but I use it as much as ever

I always do Dry January so decided to diet as well this time. No alcohol and cut way back on sugars and carbs i.e. no sweets or cakes, no bread, pasta, rice, potatoes, etc. Trying to keep to 1500 cals and to only eat between 12 noon and 6.00pm. Found it quite easy after a struggle the first few days. Routine is now sorted - cup of tea and probiotic yoghurt drink (for the stenols) in morning, big salad and protein (chicken, eggs, cold meat) with Extra Virgin and balsamic dressing for lunch and lots and lots of green veg with butter and more protein for tea. I'm a reasonable cook and have no problem eating veg, eggs and meat all the time.

Keeping track using MyFitnessPal app which is brilliant and free! Usually keep carbs down to between 50g-100g a day and sugar is about 30g or less per day. Most carbs are in the veg I eat - didnt really appreciate things like broad beans, brussel sprouts, etc had as many carbs as they did. However I need the bulk they provide so eat lots of them, doesn't make me too popular though.

Also doing 3-4 gym sessions a week involving 30 mins on bike, 60 sit ups and then weights for 40 mins. I do 8 weight stations and 4x8 reps at each, nothing too heavy, max weight I push is 50-60kgs but I try and keep pulse rate high by keeping pace up and only allowing sort intervals between reps/stations. I've lost 12lbs in just over 3 weeks so should hit target of 1st loss by end of January. Aim is to try and lose another 2st before I go on golf trip at end of April. I need to lose weight due to 58 year old dodgy knees.

I have suffered from headaches in first week or so but not sure if it is down to lack of sugar or alcohol, I suspect it is sugar withdrawals. Also felt a bit flu like but then difficult to tell with all the bugs going round if this was down to cutting back on sugar? However I now feel excellent, gym work is so much better with weight loss, I must have lost 2-3 " off my waist. I definitely feel less bloated. Actually enjoying the diet now!

TBH once I got into the routine of making lunch to go, buying the right things in the shops, etc I have not found any cravings for sugar or indeed alcohol (I would normally have a large G&T or two most nights). The only thing I find I crave is salt and savoury taste - I do find I need to add salt to my meals now whereas before I wouldn't need to. I'm using lots of pepper, herbs, chillis and spices too.

My only worry is come end of January I am tempted to have the odd drink or two, particularly with 6Ns coming up. Whilst I will avoid the pints and drink G&T slimline or malt whisky and water and count the calories inevitably the alcohol will lead to the munchies at worst time of day. Tempted to keep alcohol free until end March.

I've just started a bit of Intermittent Fasting. For some reason I've struggle dot give up carbs (lazier cooking practices) this time round so I thought I'd try something else. I going for the fast for 16 hours approach so no breakfasts and eat in a 8 hour window. Yesterday was fine, but today I've felt a tiny bit of hunger, though lunch in 5 minutes.

Ive lost just over 2 and a half stone in the last 18 months by having an essentially low carb diet. Its not been too difficult and still have the ocassional splurge at the weekends. Would like to lose another half a stone in tje next 6 months but not to bothered if I remain at my present weight.

I've just started a bit of Intermittent Fasting. For some reason I've struggle dot give up carbs (lazier cooking practices) this time round so I thought I'd try something else. I going for the fast for 16 hours approach so no breakfasts and eat in a 8 hour window. Yesterday was fine, but today I've felt a tiny bit of hunger, though lunch in 5 minutes.

Still doing this?

I'm thinking of doing time restricted feeding, although it won't take much of a change from what I've been doing the last 2 to 3 weeks. I have carbs for breakfast in the form of bran but no stodge after that. Never have lunch due to work, and have a snack of say mixed nuts, grapes and cottage cheese when I get home, and then have meat or fish with salad a couple of hours later. If I do the TRF lark then I'll just make sure I don't eat past around 7pm. I've seen some very interesting stuff from Dr Jason Fung and others on YT today.

Why do you guys feel like you need to cut out sugar entirely? I have manged to lose 15kgs just from eating less and doing some running and a bit of weights. I still treat myself from time to time, had a donut for lunch today for example. Everything in moderation. Sitting around 71kg from my peak of 86kg.

Why do you guys feel like you need to cut out sugar entirely? I have manged to lose 15kgs just from eating less and doing some running and a bit of weights. I still treat myself from time to time, had a donut for lunch today for example. Everything in moderation. Sitting around 71kg from my peak of 86kg.

I don't think you need to cut it out entirely but given how much sugar is in everyday processed that used to be considered healthy e.g. most breakfast cereals, trying to cut sugar just steers you towards more healthy 'real food' I.e. meat and veggies. Also eliminate heavy starchy carbs like bread, pasta and white potatoes and the weight just drops off.

Unfortunately eliminating/cutting down on beer, for me at least, is a different story ...